(1) Field of the Invention
The present invention relates to a technical field of a playlist playback technology.
(2) Description of the Related Art
The playlist is information defining a logical playback path. In various application formats for storing contents, the playlist is used as a unit of playback. In general, the playlist is composed of playitems and sub-playitems. The playitem is a logical playback section that is defined by specifying a pair of an in point and an out point in a time axis of a video stream that constitutes a main video image.
The sub-playitem is a logical playback section that is defined by specifying a pair of an in point and an out point in a time axis of a sub-stream. Here, the sub-stream is any of an audio stream, video stream, and subtitle stream that is not multiplexed with a video stream, but is played back together with the video stream.
When a virtual package is constructed from a combination of contents recorded on a ROM disc and another recording medium, it is possible to define, with use of the sub-playitem, a playback section of a sub-stream that is downloaded via a network. Here, it is possible to use the playitem in the playlist to define a playback section of an AV stream recorded on a ROM disc, and to use the sub-playitem in the playlist to define a playback section of a sub-stream to be downloaded. With such usage, the playlist achieves a new combination of subtitle, audio and moving image which is not achieved by optical discs.
As one example, Patent Document 1 identified below discloses a technology for generating a virtual package.
[Patent Document 1]
Japanese Patent Application Publication No. 2006-109494